Electric switch



MKM@ N Irwemr fr-neg E. J. GALLAGHER, 3D

ELECTRIC SWITCH Filed June 24, 1940 Dec. 2, 1941.

Patented Dec. 2, 1941 ELECTRIC SWITCH Edward J. Gallagher, 3rd, Doylestown, Pa., as-

signor to Struthers Dunn, Inc., Philadelphia, Pa., a corporation ot Pennsylvania Application June 24, 1940, Serial No. 342,032

(Cl. 20o-112) 3 claims.

This invention relates to an improvement in electric switches and more particularly to an lmprovement in mercury tube switches. g

The mercury switch in accordance with this invention will be so constructed as to be normally g closed without, however, the inclusion in its structure of any springs or the weighting of moving parts as customary heretofore. Again, the switch will be so constructed as to avoid hum in changing from closed to open position under the influence of the usual electromagnet; and the structure will be such as to eliminate arcing with resultant pitting when the switch is opened.

Having now rindicated in a general way the nature and purpose of this invention, I will proceed to a detailed description of a preferred embodiment thereof with reference to the accompanying drawing, in which: y

Figure l illustrates, in cross-section, a mercury switch embodying this invention, the switch as shown being closed.

Figure 2 ilustrates the switch shown in Figure 1 in open position.

In the drawing, 2 indicates a sealed tube or container of cylindrical form. The tube 2 may be conveniently made of glass. Let into the ends of the tube 2 are terminals 3, 3' of any suitable conducting material and which are adapted to be connected into an electric circuit, as by connection with the binding posts 4, 4. Contained within the lower portion of the tube 2 is a body of mercury 5, in which normally iloats a plunger comprising a body of insulating material 6 within a cylindrical metal casing l. 'Ihe metal casing 'I is provided on its outer surface with extensions 8 adapted in cooperation with the inner wall of the tube 2 to guide the plunger in movement axially of the tube.

The body of insulating material 6 is formed with a cuplike depression at its upper end adapted to contain a body of mercury 9, and an electrode I extends through the body of insulating material from contact with the body of mercury 9 to contact with the body of mercury 5, in which the plunger normally floats.

Secured to the lower end of the upper terminal 3 is a cup I I formed from insulating material and adapted, when the switch is in open position, to

carry a body of mercury I5. Normally the cupis positioned beneath the surface of the body of mercury 9. Adjacent the lower end of the tube 2 and supported by a frame I2, is an electromagnet comprising a coil I3 and a magnetic core Il.

The tube 2, the electromagnet and the binding posts 4, 4' may, as will be obvious, be arranged and mounted on a suitable base.

Normally, as has been indicated, the switch will be closed, connection between the terminals 3, 3' being made through the body of mercury 9, the electrode I0 and the body of mercury 5.

When it is desired to open the switch the electromagnet is energized and when energized will act to draw the plunger down into the body of mercury 5 a distance such that the rim of the cup II will be clear of the surface of the body of mercury 9.

In the opening of the switch as the plunger descends into the body of mercury 5, under the inuence of the electromagnet, any tendency of the plunger to chatter or hum will be damped by the body of mercury and, as will be noted, the break will occur between the body of mercury 9 and mercury contained within the connes of the cup II, which, when the rim of the cup clears the upper surface of the body of mercury 9 and the switch is open, will become an independent body of mercury I5.l

As will be noted, by reference to Figure 2, the body of mercury 5 in which the plunger floats will be displaced above the top of the plunger when the plunger is drawn down to open the switch, in order to replace or supplant the body of mercury 9, on opening of the switch, should more or less of it be lost through jarring of the switch or otherwise.

Finally, it will be noted that the switch will normally be in, and so long as the magnet remains deenergized will remain in, closed position by virtue of the flotation of the plunger in the body of mercury 5 and without other` mechanical expedient.

It will be understood that the particular embodiment of this invention as above described .for illustrative purposes may be variously modied in detail without departing from the scope of this invention.

What I claim and desire to protect by Letters Patent is:

1. A mercury switch comprising a sealed tube, a body of mercury in the tube, a plunger adapted normally to float in said body of mercury, a body of mercury carried by said plunger, in its upper end means carried by said plunger for electrically connecting said bodies of mercury, an electromagnet adapted when energizedv to draw said plunger into the body of mercury in the tube, said plunger and said body of mercury in said tube being so proportioned that when said magnet is energized the body of merciu'y in said tube will be displaced by said plunger above the upper end of the plunger whereby the body of mercury carried by the plunger will be replenished, a terminal in contact with the body of mercury in said tube, a second terminal positioned to contact with the body oi mercury carried by said plunger when said plunger is floating and to be out of contact with said body of mercury when said electro-A magnet is energized and said plunger is drawn into the body of mercury in said tube.

2. A mercury switch comprising a sealed tube, a body of mercury in the tube, a plunger adapted normally to iloat in said body of mercury, a body of mercury carried by said plunger, in its upper end, means carried by said plunger for electrically connecting said bodies oi mercury, an electromagnet adapted when energized to draw said plunger into the body of mercury in the tube, said plunger and said body of mercury in said tube being so proportioned that when said magnet is energized the body of mercury in said tube will be displaced by said plunger above the upper end of the plunger whereby the body of mercury carried by the plunger will be replenished, a terminal in contact with the body of mercury in said tube, a second terminal, a cup of insulating material carried by said second terminal and positioned so that it will rest beneath the surface of the body of `mercury carried by said plunger when plunger is drawn into the body of mercury in said tube.

3. A mercury switch comprising a sealed tube. a body ot mercury in the tube, a plunger having an inner, non-magnetic core portion recessed from its upper end. and an outer magnetic portion, the said plunger being adapted normally to iloat in said body oi mercury. a body of mercury carried within the recess in the upper end oi the core portion of said plunger, an electrode extending through the core portion oi said plunger between ysaid bodies of mercury for electrically connecting said bodies of mercury, an electromagnet adapted when energized to draw said plunger into the body of mercury in the tube, said plunger and said body of mercury in said tube being so proportioned that when said magnet is energized the body of mercury in said tube will be displaced by said plunger above the upper end of the plunger whereby the body of mercury carried by the plunger will be replenished, a terminal in contact with the body of mercury in said tube, a second terminal, a cup of insulating material carrled by said second terminal and positioned so that it will rest beneath the surface of the body of mercury carried by said plunger when said plunger is oating and so that its rim will be clear of the surface of said body of mercury when said electromagnet is energized and said plunger said plunger is floating and so that its rim will 30 is drawn into the body of mercury in said tube.

be clear of the surface of said body of mercurywhen said electromagnet is energized and said EDWARD J. GALLAGHER, 3RD. 

